Method and apparatus for assigning resources in a wireless system with multiple regions

ABSTRACT

A method and apparatus of signaling radio resource allocation in a wireless communication system includes transmitting at least one region boundary to a mobile station indicating a division of the time-frequency resources into at least two regions, determining a time-frequency resource assignment for the mobile station, transmitting an indication of the determined time-frequency resource to the mobile station in the same region as the determined time-frequency resource, and transmitting a packet to the mobile station using the physical time-frequency resources corresponding to the determined time-frequency resource.

This application claims priority to U.S. Provisional Patent ApplicationNo. 60/944,466 filed Jun. 15, 2007, entitled “Method and Apparatus ForAssigning Resources In A Wireless System with Multiple Regions” whichapplication is hereby incorporated herein by reference.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to the following provisional U.S. patentapplications, each of which is incorporated herein by reference: U.S.Provisional Patent Application No. 60/944,462 filed Jun. 15, 2007; U.S.Provisional Patent Application No. 60/944,469 filed Jun. 15, 2007; andU.S. Provisional Patent Application No. 60/944,477 filed Jun. 15, 2007.Further, this application is related to the following non-provisionalpatent applications, each of which is incorporated herein by reference:U.S. patent application Ser. No. 12/134,025, filed Jun. 5, 2008; U.S.patent application Ser. No. 12/135,599, filed Jun. 9, 2008; and U.S.patent application Ser. No. 12/135,916, filed Jun. 9, 2008.

FIELD OF THE INVENTION

The present invention generally relates to allocation of radio resourcesfor transmission in a wireless communication system. Specifically, thepresent invention relates to a novel method of signaling the allocationof radio resources for transmission in, e.g., orthogonal frequencydivision multiplexing (OFDM) and orthogonal frequency division multipleaccess (OFDMA) communication systems and the resulting systems. Evenmore specifically, the present invention relates to improved efficiencyin assigning time-frequency resources to one or more mobile stations.

BACKGROUND OF THE INVENTION

In an OFDMA communication system, the time-frequency resources of thesystem are shared among a plurality of mobile stations. Since differentmobile stations have different channel conditions, quality of service(QoS) requirements, and capabilities, in some OFDMA communicationsystems, the time-frequency resources are divided into multiple regionsto facilitate different types of transmissions. For time division duplex(TDD) systems, the time domain is divided into a downlink (DL) regionand an uplink (UL) region. In some systems, the DL region and UL regionare further divided into additional regions. For example, the DL may bedivided into a partial usage of subcarriers (PUSC) region and a fullusage of subcarriers (FUSC) region such as described by the IEEE 802.16standard. Mobile stations assigned to the DL PUSC region experience lessinterference than mobile stations assigned to the DL FUSC region.Therefore, the DL PUSC region is often advantageous for mobile stationsnear the cell edge. The DL FUSC region utilizes the entire bandwidth ineach sector, thereby maximizing the spectral efficiency. The DL FUSCregion is advantageous for those mobile stations that can tolerateincreased interference relative to what would be seen in the DL PUSCregion and is therefore advantageous for mobile stations near the basestation.

The base station assigns resources to mobile stations using anassignment message, which is transmitted as part of a control channel.The assignment message typically contains an indication of the assignedchannel (channel identifier) and other parameters related to thetransmission of a particular packet or series of packets. If multipleregions exist, it is known for the assignment message to explicitlyindicate the region, either through additional bits in the overheadmessage or by embedding the region information in the channelidentifier. An indication of the region, whether explicitly indicated orincluded as part of the channel identifier, creates additional controlchannel overhead. For wireless systems, it is essential that controlchannel overhead be carefully managed. Thus, there is a need forassigning time-frequency resources in a system with multiple regionswithout indicating the region.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides for a method of assigningtime-frequency resources in a wireless communication system. The methodincludes transmitting at least one region boundary to a mobile station,the at least one region boundary indicating a division of thetime-frequency resources into at least two regions, and determining atime-frequency resource assignment for the mobile station. The methodfurther includes transmitting an indication of the determinedtime-frequency resource assignment to the mobile station in a sameregion as the determined time-frequency resource, and transmitting apacket to the mobile station using the physical time-frequency resourcescorresponding to the determined time-frequency resource.

In another aspect, the present invention provides for a method ofreceiving a radio resource assignment in a wireless communication systemincluding receiving at least one region boundary indicating a divisionof the radio resources into at least two regions, processing a controlchannel in a first one of the at least two regions, and receiving aradio resource assignment in the first one of the at least two regions.The method further includes receiving a communication packet on thephysical radio corresponding to the received time-frequency resourceassignment in the first one of the at least two regions.

In yet another aspect, the present invention provides for a basestation. The base includes a microprocessor and a computer readablemedium storing programming for execution by the processor. Theprogramming includes instructions to define a first region and a secondregion of time-frequency resources, including defining a boundarybetween the first region and the second region of time-frequencyresources direct the transmission of the definition of a first regionand a second region of time-frequency resources to a mobile stationduring the first region of time-frequency resources. The programmingincludes further instructions to define a time-frequency resourceassignment for the mobile station, and direct the transmission of thedefinition of the time-frequency resource assignment to the mobilestation during the first region of time-frequency resources; and directthe transmission of a communication packet to the mobile station usingthe physical time-frequency resources corresponding to the determinedtime-frequency resources during the first region of time-frequencyresources.

An advantageous feature of the present invention is that signalingoverhead can be lessened by transmitting a time-frequency resourceassignment and a time-resource region definition in the actualtime-resource region.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wireless communications network;

FIG. 2 illustrates a base station and several mobile stations from awireless communications network;

FIG. 3 illustrates an exemplary set of OFDMA time-frequency radioresources;

FIGS. 4-5 illustrate an example channel tree;

FIG. 6 illustrates the division of the time domain into downlink controland legacy, downlink PUSC, downlink FUSC, uplink legacy, and uplink PUSCregions;

FIG. 7 illustrates an exemplary base node numbering scheme for theregions defined in FIG. 6;

FIG. 8 illustrates exemplary information transmitted in a downlinkcontrol and legacy region according to one embodiment of the presentinvention;

FIG. 9 is an exemplary assignment message;

FIG. 10 illustrates exemplary information transmitted in each ofexemplary downlink regions according to one embodiment of the presentinvention;

FIG. 11 illustrates exemplary information transmitted in a downlinkcontrol and legacy region according to one embodiment of the presentinvention;

FIG. 12 illustrates exemplary assignment of preferred regions;

FIG. 13 is a flow chart for exemplary base station operation; and

FIG. 14 is a flow chart for exemplary mobile station operation.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present disclosure can be described by the embodiments given below.It is understood, however, that the embodiments below are notnecessarily limitations to the present disclosure, but are used todescribe a typical implementation of the invention.

The present invention provides a unique method and apparatus forassigning resources in a wireless system with multiple regions. It isunderstood, however, that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof the invention. Specific examples of components, signals, messages,protocols, and arrangements are described below to simplify the presentdisclosure. These are, of course, merely examples and are not intendedto limit the invention from that described in the claims. Well knownelements are presented without detailed description in order not toobscure the present invention in unnecessary detail. For the most part,details unnecessary to obtain a complete understanding of the presentinvention have been omitted inasmuch as such details are within theskills of persons of ordinary skill in the relevant art. Detailsregarding control circuitry described herein are omitted, as suchcontrol circuits are within the skills of persons of ordinary skill inthe relevant art.

FIG. 1 is a wireless communications network comprising a plurality ofbase stations (BS) 110 providing voice and/or data wirelesscommunication service to respective pluralities of mobile stations (MS)120. A BS is also sometimes referred to by other names such as accessnetwork (AN), access point (AP), Node-B, etc. Each BS has acorresponding coverage area 130. Referring to FIG. 1, each base stationincludes a scheduler 140 for allocating radio resources to the mobilestations. Exemplary wireless communication systems include, but are notlimited to, Evolved Universal Terrestrial Radio Access (E-UTRA)networks, Ultra Mobile Broadband (UMB) networks, IEEE 802.16 networks,and other OFDMA based networks. In some embodiments, the network isbased on a multiple access scheme other than OFDMA. For example, thenetwork can be a frequency division multiplex access (FDMA) networkwherein the time-frequency resources are divided into frequencyintervals over a certain time interval, a time division multiplex access(TDMA) network wherein the time-frequency resources are divided intotime intervals over a certain frequency interval, and a code divisionmultiplex access (CDMA) network wherein the resources are divided intoorthogonal or pseudo-orthogonal codes over a certain time-frequencyinterval.

FIG. 2 illustrates one base station and several mobile stations from thewireless communications network of FIG. 1. As is known in the art, thecoverage area, or cell, of a base station 260 can be divided into,typically, three sub-coverage areas or sectors, one of which is shown270. Six exemplary mobile stations 200, 210, 220, 230, 240, 250 are inthe shown coverage area. The base station typically assigns each mobilestation one or more connection identifiers (CID) (or another similaridentifier) to facilitate time-frequency resource assignment. The CIDassignment can be transmitted from the base station to the mobilestation on a control channel, can be permanently stored at the mobilestation, or can be derived based on a mobile station or base stationparameter.

FIG. 3 schematically illustrates an exemplary set of OFDMAtime-frequency radio resources. In OFDMA systems, the time-frequencyresources are divided into OFDM symbols and OFDM subcarriers forallocation to respective mobile stations by a base station scheduler. Inan exemplary OFDMA system, the OFDM subcarriers are approximately 10 kHzapart and the duration of each OFDM symbol is approximately 100 μsec.FIG. 3 illustrates one 5 msec frame of an OFDMA system, such as thatdefined by the IEEE 802.16e standard. Referring to FIG. 3, in thisexemplary embodiment, resources in the time domain (x-axis) are dividedinto 48 OFDM symbols 320. In the frequency domain (y-axis), theresources are divided into multiple subchannels (not shown), wherein thesize of the subchannel depends on the subcarrier permutation scheme, aswill be discussed in more detail later.

FIGS. 4-5 illustrate an exemplary channel tree, which is used tologically illustrate the division of time-frequency resources. Referringto FIG. 4, the main parent node, labeled as node 0, represents theentire set of time-frequency resources. In this channel tree, each nodeis sub-divided into two nodes. Therefore, the main parent node, node 0,is sub-divided into parent nodes 1 and 2. Parent nodes 1 and 2 eachrepresent fifty percent of the entire set of time-frequency resources.The lowest level nodes (nodes 127, 128, 129, . . . , 254) are referredto as base nodes. A base node represents the smallest time-frequencyresource that can be allocated to a mobile station using the channeltree. The collection of nodes under parent node 15, enclosed by 420, isenlarged and depicted in FIG. 5. Referring to FIG. 5, parent node 15 isdivided into parent nodes 31 and 32. Parent node 31 is divided intoparent nodes 63 and 64, and parent node 32 is divided into parent nodes65 and 66. Parent node 63 is divided into base nodes 127 and 128, parentnode 64 is divided into base nodes 129 and 130, parent node 65 isdivided into base nodes 131 and 132, and parent node 66 is divided intobase nodes 133 and 134.

Each channel tree node corresponds to a physical portion of thetime-frequency resources. For example, consider an OFDMA systemcontaining 384 useful subcarriers, indexed 0 to 383. In one exemplarychannel tree configuration, node 0 corresponds to subcarriers 0 through383, node 1 corresponds to subcarriers 0 through 191, and node 2corresponds to subcarrier 192 through 384. In another exemplary channeltree configuration, node 0 corresponds to subcarriers 0 through 383,node 1 corresponds to subcarriers 0, 2, 4, . . . , 382, and node 2corresponds to subcarrier 1, 3, 5, . . . , 383. The mapping of logicalchannel tree nodes to physical time-frequency resources may change withtime and may be different in different sectors. Any mapping of logicalchannel tree nodes to physical time-frequency resources is possible, aslong as the mapping scheme is known at the base station and the mobilestation. The mapping scheme can be stored at a base station and a mobilestation, transmitted to a mobile station from a base station, determinedat a mobile station based on a parameter received from a base station,combinations of the above, and the like.

FIG. 6 illustrates the division of the time domain into three downlinkregions 610, 620, and 630 and two uplink regions 640, 650. Referring toFIG. 3, note that there are 48 OFDM symbols in each 5 msec frame. FirstDL region 610 is denoted the DL control and legacy region and preferablyhas a duration of 3 OFDM symbols. Second DL region 620 is denoted the DLPUSC region and preferably has a duration of 6 OFDM symbols. Third DLregion 630 is denoted the DL FUSC region and preferably has a durationof 15 OFDM symbols. First UL region 640 is denoted the UL legacy regionand has a duration of 24 OFDM symbols in the illustrated example. SecondUL region 650 is denoted the UL PUSC region and has a duration of 24OFDM symbols in the illustrated example. Note that the guard intervalbetween the DL and UL regions is ignored for illustration, althoughthose skilled in the art will recognize the need and typicalconfiguration of a guard region in the frame. Referring to FIG. 6, thethree DL regions contain 24 OFDM symbols collectively, and the two ULregions contain 24 OFDM symbols collectively. As will be discussed inmore detail later, preferred embodiments of the invention provide a newcontrol mechanism. Some mobile stations, denoted new mobile stations, inthe system will be able to interpret this new control mechanism whileother mobile stations, denoted legacy mobile stations, in the systemwill not be able to interpret this new control mechanism. In FIG. 6, thelegacy mobile stations will be served in DL legacy region 610 and ULlegacy region 650, as is known in the art.

Within each region, subcarrier permutations are defined by the basestation. DL PUSC, DL FUSC, and UL PUSC are exemplary subcarrierpermutations schemes defined in the IEEE 802.16 standard. Otherpermutation schemes are also defined in the IEEE 802.16 standard; DLPUSC, DL FUSC, and UL PUSC are merely used to illustrate the invention.Any subcarrier permutation scheme could be used in each region. Forexemplary DL PUSC region 620, there are preferably 360 data subcarriersdivided into 15 subchannels, wherein each subchannel has 24 subcarriers.For DL PUSC region 620, the base station preferably assigns an evennumber of OFDM symbols for each subchannel. For exemplary DL FUSC region630, there are preferably 384 data subcarriers divided into 8subchannels, wherein each subchannel has 48 subcarriers. For exemplaryUL PUSC region 650, there are preferably 408 subcarriers (data pluspilot) divided into 17 subchannels, wherein each subchannel has 24subcarriers (16 data plus 8 pilot). For UL PUSC, the number of OFDMsymbols for each subchannel is preferably a multiple of 3.

Once regions are defined, the base station transmits assignment messagesto mobile stations to indicate particular time-frequency resourceassignments. There are several ways for allocating radio resources. FIG.7 provides an exemplary technique for allocating radio resources,wherein the time-frequency resources are divided into base nodes and achannel tree structure, such as the channel tree structure of FIGS. 4-5,is used to indicate time-frequency resource assignments. Referring toFIG. 7, unique channel trees are preferably used in each region. DL PUSCregion 720 has base nodes numbered 15-30, DL FUSC region 730 has basenodes 63-126, and UL PUSC region 750 has base nodes numbered 31-62. Someof the base nodes are imaginary base nodes 760, wherein imaginary basenodes 760 are used to maintain a tree structure and do not correspond toany physical time-frequency resources. DL control and legacy region 710and UL legacy region 740 are not shown to have channel trees, sincelegacy mobile stations will typically not be able to interpret thechannel tree, although a channel tree can be defined in these regionsfor the mobile stations that do understand the channel tree in order tomultiplex new mobile stations with legacy mobile stations. Within eachregion, a channel tree is constructed with the size of the channel treedependent on the size of the region and the size of a base node. Theseparameters determine the number of base nodes in the region, andtherefore the overall size of the channel tree. For example, the channeltree in DL PUSC region 720 is 5 levels “deep” (referring back to FIG. 4,it can be seen that parent node 0 is at a first level, nodes 1 and 2 areat a second level, nodes 3-6 are at a third level, nodes 7-14 are at afourth level, and nodes 15-30 are at a fifth level), and can be indexedwith 5 bits. The channel tree in DL FUSC region 730 has 7 levels and canbe index with 7 bits.

To establish the regions of FIGS. 6-7, the base station transmits onemore region definition messages to the mobile stations. FIG. 8 providesan exemplary location for transmitting the region definition messages.Referring to FIG. 8, DL control and legacy region 610 preferably containfour types of information (as well as other information not shown).First, DL control and legacy region 610 contains one or more regiondefinition messages 810, one or more DL traffic assignments 830, one ormore UL traffic assignments 820, and one or more DL traffic transmission840. Region definition messages 810 may contain one or more of thefollowing: region starting point, region ending point, region width, andregion subcarrier permutation. Region definitions can be dependent onother each other or can be independent. For example, referring to FIGS.6-7, a base station can transmit an indication of OFDM symbol 3 and anindication of the DL PUSC subcarrier permutation using a regiondefinition message 810 to define DL PUSC region 720. Likewise, a basestation and can transmit an indication of OFDM symbol number 9 and anindication of the DL FUSC subcarrier permutation using a regiondefinition message 810 to define DL FUSC region 730. The mobile stationspreferably determine the ending point of DL PUSC region 720 based on thestarting point of DL FUSC region 730. In other embodiments, the startingpoint of one region can be determined based upon the ending point of anadjacent region, as will be apparent to those skilled in the art.Alternatively, the base station can include the number of OFDM symbolsin each region definition message 810 to eliminate the interdependence.Multiple regions can be defined in each region definition message 810 oreach region definition message 810 can include one region definition.

Once a base station establishes regions, the base station transmits DLtraffic assignments 830 and UL traffic assignments 820 in order toallocate time-frequency resources to the mobile stations. Theassignments are typically generated in a base station scheduler (such asbase station scheduler 140 illustrated in FIG. 1). FIG. 9 providesfields of an exemplary assignment message 910, which can be either DLtraffic assignments 830 or UL traffic assignments 820. Referring to FIG.9, the assignment message 910 preferably contains a 16 bit fieldindicating connection identifier 912 of the mobile station, whereinconnection identifier 912 corresponds to one or more mobile stations.Typically, connection identifier 912 corresponds to a single mobilestation, but in the case of a multi-cast or broadcast transmission,connection identifier 912 could correspond to several mobile stations.Note that, in some embodiments, connection identifier 912 is notincluded in assignment message 910, but is rather used to scrambleassignment message 910. In this way, only the intended mobile stationcan correctly decode assignment message 910. Assignment message 910 alsopreferably contains a 3 bit region identifier field 913 and a 7 bitchannel identifier field 914, wherein the region identifier correspondsto a region and the channel identifier corresponds to one of the nodesfrom a channel tree. Note that, in this example, channel identifierfield 912 is preferably set to the maximum number of bits needed torepresent the channel trees of FIG. 7, in order to have a constantassignment message 910 size. Assignment message 910 preferably alsocontains a multiple input multiple output (MIMO) field 915 forindicating parameters related to the MIMO scheme. MIMO field 915 is usedto indicate the type of MIMO parameters used by a base station, such asprecoding scheme, antenna configuration, and the like. Finally,assignment message 910 may contain a four bit field indicatingmodulation and coding 916 of the packet. It should be clear to thoseskilled in the art that there are a variety of ways of communicating theparameters delineated in FIG. 9. While one or more of these parametersare preferably communicated to the mobile station, not all parametersare used in all embodiments, and some parameters can be omitted based onthe value of other parameters.

As an illustrative example of a DL traffic assignment 830, an exemplarybase station can assign a mobile station with CID ‘0100100101010101’ tochannel tree node 29 (binary ‘0011101’) in the DL PUSC region 720 (theDL PUSC region 720 is the second region where ‘000’ corresponds to thefirst region, ‘001’ corresponds to the second region, etc) using theassignment message 910. To make this assignment, the base station setsConnection Identifier field 912 to ‘0100100101010101’, Region Identifierfield 913 to ‘001’, Channel Identifier field 914 to ‘0011101’, and MIMOfield 915 and modulation/coding field 916 to the appropriate values asis well known in the art.

DL traffic assignments 830 and UL traffic assignments 820 represent asignificant portion of the control channel overhead of the system. Sincereducing control channel overhead is important for wirelesscommunication systems, FIG. 10 illustrates a mechanism for reducing thecontrol channel overhead by eliminating some of the bits in theassignment message 910. Referring to FIG. 10, DL traffic assignments1010 and 1050 are moved from DL control legacy region 610 to each of DLPUSC region 620 and DL FUSC region 630, respectively. In this way, thebase station does not need to transmit an indication of the region tothe mobile station, since assignments for each region are carried withinthe region. In addition, the number of bits for indicating the channelidentifier can be exactly what is needed to represent the channel treein that specific region. Exemplary assignment messages 1090 and 1095 forDL PUSC 620 region and DL FUSC 630 region are provided to illustratethese advantages. Referring to FIG. 10, assignment message 1090 does notinclude a region identifier and includes 5 bits for indicating thechannel identifier 1092. Assignment message 1095 does not include aregion identifier and includes 7 bits for indicating the channelidentifier 1097. Mobile stations determine the size of the assignmentmessage in the respective region based on the parameters with fixed size(connection identifier, MIMO, Modulation/Coding) plus the parameterswith a size that is dependent on the region definition (channelidentifier). In some embodiments, certain fields are only included forcertain region types. For example, the MIMO field could be omitted forDL PUSC regions.

Assignments for uplink transmissions are carried on the downlink.Therefore, each uplink region must be associated with a downlink region.For example, assignments for UL PUSC region 650 can be transmitted in DLFUSC region 630. These assignments can be made using the UL trafficassignments 1070 for DL FUSC region 630. The term corresponding regionswill be used to denote the relationship between a DL region in which aUL assignment is made and a UL region in which a UL assignment is valid.

If assignment messages are located within the same region as the datatransmission, the mobile station must decode assignment messages in eachregion in order to determine if it is assigned a time-frequencyresource. This is not as desirable as the case where assignment messageare transmitted at the beginning of the frame, since this approach doesnot allow a mobile station to enter a reduced power mode after decodingthe assignment message. To mitigate this problem, two solutions areproposed (at a beginning of a frame). FIG. 11 illustrates a preferredsolution.

Referring to FIG. 11, the base station includes a CID list 1150 or ahashed bitmap 1160 in the DL control and legacy region 610. The mobilestations determine if they are assigned a time-frequency resource in thecurrent frame by processing either the CID list 1150 or the hashedbitmap 1160. The CID list 1150 may only include the N least significantbits of each CID. When the CID list 1150 is transmitted in the DLcontrol and legacy region 610, the mobile stations determine if theirCID matches a CID from the CID list 1150. If so, the mobile stationsprocess the DL traffic assignments in each region. If not, the mobilestation can enter a reduced power state until the next frame. When thehashed bitmap 1160 is transmitted in DL control and legacy region 610,the mobile station apply a hashing algorithm to their CID and if a matchis determined with one or more values in hashed bitmap 1160, the mobilestation process the DL traffic assignments in each region. If not, themobile station can enter a reduced power state until the next frame.Also shown in FIG. 11 are: field 1110, where zone definitions can beprovided, field 1120, where UL traffic assignments are provided, field1130 where DL traffic assignments are provided, and field 1140 whereinis provided the DL traffic.

FIG. 12 illustrates an alternative solution to that illustrated in FIG.11. In some embodiments, the overhead associated with CID list 1150 orhashed bitmap 1160 is not desirable. Therefore, each mobile station isassigned one or more preferred regions in this embodiment. The preferredregion assignment is typically transmitted using higher layer signalingand can be a region identifier, region type, and the like. For example,a base station can indicate to a mobile station that its preferredregion is “DL PUSC.” Alternatively, a base can indicate to a mobilestation that its preferred region is ‘001’, where ‘001’ corresponds tothe second region. FIG. 12 provides exemplary assignments of preferredregions to multiple mobile stations. Referring to FIG. 12, MS₅ and MS₁are each assigned DL PUSC region 1220 as their respective preferredregion. MS₃ is assigned both DL PUSC region 1220 and DL FUSC region 1230as its preferred regions. MS₀, MS₂, and MS₄ are each assigned DL FUSCregion 1230 as their respective preferred region. Once the mobilestations are assigned a preferred region, the mobile stations thenmonitor the DL traffic assignments only in their respective preferredregion(s). In some embodiments, each mobile station monitors the DLcontrol and legacy region 1210, which allows base station to makeassignments in any region using the normal assignment message, such asassignment message 910.

Once preferred regions are established as in FIG. 12, a base station canrelocate an entire set of assignment messages to a new region, denotedthe control region. Then, the mobile station processes the assignmentmessages under the hypothesis that the message has the fields associatedwith its preferred region(s). Again, in some embodiments, some of thefield lengths are determined from the region length. If the mobilestation is able to successfully decode the assignment message, it knowsthat the region for which the assignment is valid is the preferredregion of the mobile station. If a mobile station has more than onepreferred region, the base station can differentiate between the regionsusing unique scrambling, if the number of bits in the assignmentmessages for the multiple regions are the same. Exemplary UL region ispreferably divided into a 24 symbol legacy UL region 1240 and a 24symbol UL PUSC region 1250. One skilled in the art will recognize otherconfigurations and permutations for UL region are equally possible.

FIG. 13 is a flow chart for exemplary base station operation. At step1310, a base station divides time-frequency resources into two or moreregions, wherein each region is identified by at least one regionboundary. The region boundaries can be an OFDM symbol number, an offsetfrom another region, and the like. At step 1320, the base stationtransmits an indication of at least one region boundary to a mobilestation. The indication can be sent on a control channel. Note that someregion boundaries can be known at the mobile station or derived at themobile station based on a parameter received from the base station. Atstep 1330, the base station determines a time-frequency resourceassignment for a mobile station. The assignment is typically determinedby a base station scheduler and can be an index to a channel tree, anexplicit indication of OFDM symbols and OFDM subchannels, and the like.At step 1340, the base station transmits an indication of the determinedtime-frequency resource in the same region as the determinedtime-frequency resource for DL assignments and in a region correspondingto the determined time-frequency resource for UL assignments. At step1350, the base station transmits a packet to the mobile station orreceives a packet from the mobile station on the physical time-frequencyresources corresponding to the determined time-frequency resource.

FIG. 14 is a flow chart for exemplary mobile station operation. At step1410, the mobile station receives an indication of at least one regionboundary from the base station. At step 1420, the mobile stationprocesses one or more control channels in at least one of the regions todetermine if a time-frequency resource has been assigned. The controlchannels can be DL assignment or UL assignments as previously described.At step 1430, the mobile station determines the assigned time-frequencyresource as the time-frequency resource within the region in which thecontrol channel was received for DL assignments and within the regioncorresponding to the region in which the control channel was receivedfor UL assignments. At step 1440, the mobile station transmits a packetto the base station or receives a packet from the base station using thephysical time-frequency resources corresponding to the determinedtime-frequency resource.

One skilled in the art will recognize that the terms base station,mobile station, and the like are intentionally general terms and are notto be interpreted as limited to a particular system, protocol,communications standard, or the like. Those skilled in the art will alsorecognize that the various methods and steps described herein can beaccomplished by a radio device, such as a base station including eithera general purpose or a special purpose processor appropriatelyprogrammed to accomplish, e.g., the presently described methods andsteps. The base station preferably includes storage medium for storingprogramming instructions for the processor.

Although specific embodiments of the present invention have beendescribed, it will be understood by those of skill in the art that thereare other embodiments that are equivalent to the described embodiments.Accordingly, it is to be understood that the invention is not to belimited by the specific illustrated embodiments, but only by the scopeof the appended claims.

What is claimed is:
 1. A method of assigning time-frequency resources ina wireless communication system, the method comprising: transmitting atleast one region boundary to a mobile station, the at least one regionboundary indicating a division of the time-frequency resources into atleast two regions; determining a time-frequency resource assignment forthe mobile station; transmitting an indication of the determinedtime-frequency resource assignment to the mobile station in a sameregion as the determined time-frequency resource; and transmitting adata packet to the mobile station using the physical time-frequencyresources corresponding to the determined time-frequency resource in thesame region of the determined time-frequency resource.
 2. The method ofclaim 1, further comprising transmitting an indication of at least onepreferred region to the mobile station.
 3. The method of claim 1,wherein the wireless communication system is an orthogonal frequencydivision multiplexing based (OFDMA-based) system.
 4. The method of claim1, wherein transmitting an indication of the determined time-frequencyresource assignment to the mobile station in the same region as thedetermined time-frequency resource includes transmitting at least oneof: a connection identifier; a channel identifier; a MIMO parameteridentifier; and a modulation coding parameter identifier.
 5. The methodof claim 1, wherein the at least two regions include a downlink regionand an uplink region.
 6. The method of claim 1, wherein the at least tworegions include a downlink partial usage of subcarriers (PUSC) region, adownlink full usage of subcarriers (FUSC) region, and an uplink PUSCregion.
 7. The method of claim 1, wherein the at least two regionsfurther includes a downlink control region.
 8. The method of claim 7,further comprising transmitting an indication of the determinedtime-frequency resource assignment to a mobile station in the downlinkcontrol region.
 9. The method of claim 1, further comprising identifyingan OFDM symbol at which the at least one region boundary occurs.
 10. Abase station comprising: a processor; a computer readable medium storingprogramming for execution by the processor, the programming includinginstructions to: define a first region and a second region oftime-frequency resources, including defining a boundary between thefirst region and the second region of time-frequency resources; direct atransmission of the definition of a first region and a second region oftime-frequency resources to a mobile station during the first region oftime-frequency resources; define a time-frequency resource assignmentfor the mobile station; direct a transmission of the definition of thetime-frequency resource assignment to the mobile station during thefirst region of time-frequency resources; and direct a transmission of adata packet to the mobile station using the physical time-frequencyresources corresponding to the determined time-frequency resourcesduring the first region of time-frequency resources.
 11. The basestation of claim 10, wherein the processor is a collection of aplurality of processors working in concert.
 12. The base station ofclaim 10, wherein defining a boundary between the first region andsecond region of time-frequency resources comprises identifying an OFDMsymbol at which the boundary occurs.
 13. The base station of claim 10,wherein the second region of time-frequency resources is definedrelative to the end of the first region of time-frequency resources. 14.The base station of claim 10, wherein the programming further includesinstructions to direct a transmission of an indication of at least onepreferred region to the mobile station.
 15. The base station of claim10, wherein the base station is an orthogonal frequency divisionmultiplexing (OFDMA) base station.
 16. The base station of claim 10,wherein the programming including instructions to direct thetransmission of the definition of the time-frequency resource assignmentto the mobile station during the first region of time-frequencyresources further includes instructions to transmit at least one of: aconnection identifier; a channel identifier; a MIMO parameteridentifier; and a modulation coding parameter identifier.
 17. The basestation of claim 10, wherein the first and second regions include adownlink region and an uplink region.
 18. The base station of claim 10,wherein the first and second regions comprise regions selected from thegroup consisting of a downlink partial usage of subcarriers (PUSC)region, a downlink full usage of subcarriers (FUSC) region, an uplinkPUSC region, a control region, an uplink legacy region.
 19. The basestation of claim 10, wherein the first and second regions include adownlink control region.
 20. The base station of claim 18, wherein theprogramming including instructions to direct the transmission of thedefinition of the time-frequency resource assignment to the mobilestation during the first region of time-frequency resources furtherincludes instructions to direct the transmission in the downlink controlregion.